The invention relates to a method for producing a magnet unit for a sensor device for detecting a measurement variable which is characteristic of a state of rotation of a steering shaft of a motor vehicle. A ring-shaped magnet element composed of a plastics-bonded magnet material is provided. Furthermore, a carrier sleeve—composed for example of metal—is provided, by way of which the magnet unit can be connected to a shaft part of the steering shaft. The magnet element and the carrier sleeve are then, in particular axially adjacent to one another, connected to one another by way of respective axial face sides. The invention also relates to a magnet unit for a sensor device of a motor vehicle, having a ring-shaped magnet element and having a carrier sleeve which is connected to the magnet element and by way of which the magnet unit can be connected to a shaft part. The invention also relates to a sensor device and to a motor vehicle.
Torque sensor devices for detecting a torque applied to a steering shaft of a motor vehicle are already prior art. Such torque sensor devices may be used for example in electric steering systems. A torque sensor device of said type is known for example from the document US 2004/0194560 A1 and from the document DE 102 40 049 A1. Here, the torque sensor device is attached to two shaft parts or sub-shafts of the steering shaft which are situated opposite one another in an axial direction. A magnet—for example a ring-shaped magnet—is arranged on the first shaft part, whereas a holder with a magnetic stator is attached to the other shaft part, which stator is situated opposite the permanent magnet in a radial direction with a small air gap. Via the stator—which is normally composed of two separate stator parts—the magnetic flux of the magnet is conducted to a first and to a second flux conductor, which then release the magnetic flux to a magnetic sensor—for example a Hall sensor.
A torque sensor device of said type is also known from document DE 10 2007 043 502 A1.
Furthermore, from the prior art, steering angle sensor devices are also known which serve for the detection of the present steering angle of the steering shaft. A device of said type emerges, so as to be known, for example from the document DE 10 2008 011 448 A1. A rotational movement of the steering shaft is in this case transmitted via a gearing to a relatively small gearwheel, which bears a magnet. The rotation of the relatively small gearwheel is then detected by way of a magnetic sensor.
The prior art also includes devices in which the torque sensor device, on the one hand, and the steering angle sensor device, on the other hand, are formed integrally as a common unit.